Generally, wire bonding is a method for forming connections between an integrated circuit (IC) and a package containing the IC or directly to a printed circuit board. In wire bonding, a wire is used to create an electrical connection from bonding pads on the IC and the package. The wire may be made from gold, aluminum, copper, alloys thereof, and so forth. Wire bonding is generally considered to be cost effective and flexible and is used to assemble a large percentage of semiconductor packages.
An alternate technique used for connecting ICs to external circuitry or other ICs is commonly referred to as flip chip. In flip chip, ICs are connected to other circuits, such as external circuitry or other ICs with solder bumps deposited onto chip pads. The solder bumps may be deposited on the chip chaps on a top side of a semiconductor wafer during wafer processing. The IC may then be flipped over (hence the name) so that its top surface faces down and then soldered to complete the interconnection between the IC and external circuitry or other ICs.
Flip chip replaces the bond wires used in wire bonding with solder bumps for external signal and power connections. The use of solder bumps helps to reduce a significant current-resistance (IR) drop seen in wire bonding with high power applications since long and highly resistive bond wires are eliminated. Signals and power may be distributed within a flip chip IC using stacked via structures.